A vertical axis washing machine appliance generally includes a tub with a basket rotatably positioned within the tub. Articles to be washed, such as clothes, are placed in the machine's basket. An agitation element can be included in the tub, and can rotate to move articles within the basket to facilitate washing. Agitation elements are typically impellers, single-action agitation elements or dual-action agitation elements. A single-action agitation element reciprocates about a vertical axis within the machine's basket. Typically, fins extend from a shaft of the agitation element to contact and move the articles. The fins in many cases are cantilevered or spiraled. The surface of the basket and gravity are used in conjunction with these single-action agitation elements to impart a circular motion of the articles, known as “turnover,” from a top of the basket, to a bottom of the basket, and back up to the top of the basket.
Single-action agitation elements do not, for the most part, exhibit good turnover capability due to the generally mediocre ability of gravity alone, or in conjunction with various known fin designs, to force the articles downwardly along the shaft. Accordingly, certain washing machine appliances include dual-action agitation elements. Dual-action agitation elements generally include an auger at a basket center that enhances turnover by ratcheting in one direction and actively pulling the clothing downward. However, such dual-action agitation elements are typically more expensive and more complicated to implement.
Further, some known single-action and dual-action agitation elements include ribs which extend from a base of the agitation element. Ribs are generally provided in an effort to assist in movement of articles within baskets by creating a lifting stream and pushing articles up and away from the agitation element. However, known rib designs are easily breakable and/or can cause rapid wear to articles being washed.
Accordingly, improved agitation elements are desired in the art. In particular, agitation elements which are efficient and effective at moving articles within washing machine appliance baskets and which are relatively more robust and reduce associated article wear would be advantageous.